dixie: only use sixtap mc filter

Remove all the special case 2-tap, 4-tap, 16x16, 8x8, etc filters,
and instead just use one 2D 6-tap 4x4 filter.

Change-Id: I9ec560fb5609d1a3160e9a3d8b396911073517a0

vp8/dixie/dixie.h

@@ -177,37 +177,7 @@ enum splitmv_partitioning
 };
 
 
-/* This prototype is used to match the libvpx reference assembly */
-typedef void (*mc_fn_t)(const unsigned char *reference,
-                        int                  reference_stride,
-                        int                  mx,
-                        int                  my,
-                        unsigned char       *output,
-                        int                  output_stride);
-
-enum mc_block_sz
-{
-    MC_16X16,
-    MC_8X8,
-    MC_8X4,
-    MC_4X4,
-    NUM_MC_BLOCKS
-};
-
-
-enum mc_mode
-{
-    MC_0H0V = 0,
-    MC_6H0V = 1,
-    MC_4H0V = 2,
-    MC_0H6V = 4 + 0,
-    MC_6H6V = 4 + 1,
-    MC_4H6V = 4 + 2,
-    MC_0H4V = 8 + 0,
-    MC_6H4V = 8 + 1,
-    MC_4H4V = 8 + 2,
-    NUM_MC_MODES
-};
+typedef short filter_t[6];
 
 
 typedef union mv
@@ -307,7 +277,7 @@ struct vp8_decoder_ctx
     struct ref_cnt_img             *ref_frames[NUM_REF_FRAMES];
     ptrdiff_t                       ref_frame_offsets[4];
 
-    mc_fn_t                         mc_functions[NUM_MC_BLOCKS][NUM_MC_MODES];
+    const filter_t                 *subpixel_filters;
 };